Adding support for execution on slurm grids

- Adding support for SlurmTaskExecutor in `daggyd` if DAGGY_ENABLE_SLURM is defined.
- Renaming some test cases
- Enabling compile-time slurm support
- Adding slurm documentation

tests/unit_utilities.cpp

@@ -15,13 +15,13 @@
 
 namespace fs = std::filesystem;
 
-TEST_CASE("String Utilities", "[utilities_string]") {
+TEST_CASE("string_utilities", "[utilities_string]") {
     std::string test = "/this/is/{{A}}/test/{{A}}";
     auto res = daggy::globalSub(test, "{{A}}", "hello");
     REQUIRE(res == "/this/is/hello/test/hello");
 }
 
-TEST_CASE("Parameter Expansion", "[utilities_parameter_expansion]") {
+TEST_CASE("string_expansion", "[utilities_parameter_expansion]") {
     SECTION("Basic expansion") {
         std::string testParams{R"({"DATE": ["2021-05-06", "2021-05-07" ], "SOURCE": "name", "TYPE": ["a", "b", "c"]})"};
         auto params = daggy::configFromJSON(testParams);
@@ -55,7 +55,7 @@ TEST_CASE("Parameter Expansion", "[utilities_parameter_expansion]") {
     }
 }
 
-TEST_CASE("DAG Runner", "[utilities_dag_runner]") {
+TEST_CASE("dag_runner", "[utilities_dag_runner]") {
     daggy::executors::task::ForkingTaskExecutor ex(10);
     std::stringstream ss;
     daggy::loggers::dag_run::OStreamLogger logger(ss);